HIGH AND LOW DENSITY WATER AND RESTING,ACTIVE AND TRANSFORMED CELLS

Resting and active states of cells are described in terms of the expectation, derived from experiments with aqueous polymers, that they contain two modified forms of water: high density, reactive, fluid water and low density, inert, viscous water. Low density water predominates in a resting cell and is converted to high density water in an active cell. It is proposed that switching from one state to another is an integral part of cellular function. When this ability is lost cells are transformed either to a state of rigor or to a hyperactive state in which they no longer depend upon external signals.     

FACTS AND FALLACIES ABOUT GONORRHEA AND SYPHILIS

The limitations and special usefulness of clinical and laboratory diagnostic techniques in the diagnosis of gonorrhea are poorly understood and utilized by the average practitioner today. Most physicians and clinics, lulled by complacency or lack of ancillary aid in the area of diagnosis, proceed by measures based in many instances upon past fallacy rather than upon the facts recently developed by research in this disease. The same circumstances apply concerning treatment and management of this disease, particularly in females.All physicians are potentially capable of giving excellent treatment for syphilis today. The problem is to properly diagnose the disease, manage the patient and deal with the source. Looming large in the area of diagnosis is the interpretation of serologic tests for syphilis. No serologic test diagnoses syphilis, but rather gives information as to the immunologic status of the the patient in relation to reagin and treponemal antibodies. None of the antibodies measured in these tests are absolutely specific for syphilis alone.There is no substitute for a well-informed physician, who knows his patient, to relate and interpret even the best of treponemal serologic tests.     

MEGAGAMETOPHYTE AND NUCELLUS IN RESTIONACEAE AND FLAGELLARIACEAE

Restionaceae are characterized by Polygonum-type development, a well-developed hypostase, the presence of starch grains in the mature female gametophyte, and a thick nucellus that is uniseriate at the micropylar end. Flagellaria indica differs in these characters. In general, proliferation of antipodals occurs in South African taxa of Restionaceae but not in Australasian taxa. The presence of multiplied antipodals is the usual condition in the allied family Poaceae, but the sporadic occurrence of this character in Restionaceae cannot be used to support the view that the two families are sister groups.     

THE CRETACEOUS PTERIDOSPERMS RUFLORINIA AND KTALENIA AND IMPLICATIONS ON CUPULE AND CARPEL EVOLUTION

The vegetative (Ruflorinia sierra) and fertile (Ktalenia circularis) organs of an Early Cretaceous pteridosperm collected from Santa Cruz Province in Argentina are described. The sterile leaf is at least tripinnate and bears decurrent secondary pinnae with obliquely attached, sharply pointed pinnules. The fertile member arises from the base of the vegetative rachis and bears two types of appendages, cupules and bracts. Bracts are attached to the main axis near cupules and are present in clusters of up to six. Cupules are sessile, spherical, and arranged in opposite or subopposite pairs along the axis. A small lip is present on one surface of the cupule. The number of seeds per cupule may be one or two, with each characterized by a distal nucellar beak and circular, chalazal scar. Cuticular anatomy, including the fine structure of the stomatal complex, is described for both vegetative and reproductive organs. The cupules of Ktalenia and other Mesozoic seed plants are compared, and a discussion presented regarding the possible function of the cupule.     

PROTEIN SYNTHESIS AND DEGRADATION DURING AGING AND SENESCENCE

1. The published results on protein synthesis during aging are contradictory. Possible sources of error and variability include: an insufficient number of different animal ages used; use of whole organs that are cytologically highly heterogeneous; different animal strains; neglecting to measure the specific activity of the precursor pool for protein synthesis; and inadequate methodology for measurement of in vivo rates of protein synthesis. 2. In general, protein synthesis rates in mammals have been reported to decline 4–70% with age. In insects and other organisms, greater losses (60–90%) have been observed. 3. Limited evidence indicates that in some systems a decline in the rate of protein synthesis may be due to alterations (as yet of unknown nature) in the initiation components of the protein synthetic apparatus. Futhermore, some studies suggest that in some organisms aging affects the expression of specific parts of the genome. 4. The significance of results on protein metabolism obtained from some studies with nematodes is at present unknown, owing to problems associated with age-synchronization methods. Also, the in vitro fibroblast system for the study of human cellular aging has not been met with universal acceptance; it is generally believed that this system has not yet been established as a valid analogy to mammalian aging in vivo. 5. Failure to detect defective enzymes in many old organisms indicates at least that not all proteins are altered during aging. The complete thermal stability of purified enzymes from old organisms suggests that the observed thermolability of the same enzymes in crude cell extracts is not an intrinsic property of those enzymes. Post-translational modifications (partial denaturation) may constitute the primary mechanism for the production of altered cell polypeptides during aging. 6. The available evidence does not support the concept of an age-dependent decline in translational accuracy. The future purification to absolute homogeneity of an altered enzyme and its ‘young’ (unaltered) counterpart, and their sequencing, should resolve the question of translational errors. 7. Some degree of age-related ribosome loss appears to occur in fixed postmitotic cells. In general, the published polyribosomal profiles may represent artefacts due to insufficiently suppressed ribonuclease activity during extraction. 8. The published studies on protein degradation during aging are also contradictory. Some investigators have neglected the possibility of reutilization of labelled amino acid. It is possible that some of the observed age-related alterations in protein degradation rates are due to altered endocrine status of the animals used, rather than to defects in the protein degradative pathways. The studies utilizing cell culture systems are also contradictory, probably due to different experimental designs. 9. Limited evidence suggests that protein degradation may slow down with age in mammals and nematodes. An inefficient protein degradation system in old organisms could provide an explanation for the accumulation of altered macromolecules in some organisms. Virtually nothing is known about regulatory mechanisms of protein degradation during senescence. 10. There is a need to examine which proteins are synthesized and degraded at selectively different rates as a function of age and what their physiological role is. This approach would be more informative than the study of total protein turnover with age. 11. The physiological significance, and the causes of the observed declines in protein synthesis and degradation rates during aging and senescence, remain to be established.     

ON THE DEFINITIONS AND FUNCTIONS OF DOMINANCE AND TERRITORIALITY

1. Dominance/subordinance is a relationship between two individuals in which one defers to the other in contest situations. Each such relationship represents an adaptive compromise for each individual in which the benefits and costs of giving in or not giving in are compared. Familiar associates in groups or neighbours on nearby territories may develop relatively stable dominant-subordinate relationships based on individual recognition. Although the aggressive aspects of dominance are usually emphasized, the less conspicuous actions of the subordinate individual are actually more important in maintaining a stable relationship. 2. In evolutionary terms, dominance essentially equals priority of access to resources in short supply. Usually the subordinate, who would probably lose in combat anyway, is better off to bide its time until better able to compete at another time or another place. Both individuals save time, energy, and the risk of injury by recognizing and abiding by an established dominant-subordinate relationship. 3. Dominance can be either absolute or predictably reversible in different locations or at different times. Of the various forms of dominance behaviour, rank hierarchies and territoriality represent the two extremes of absolute and relative dominance, respectively. A dominance hierarchy is the sum total of the adaptive compromises made between individuals in an aggregation or organized group. Many animals seem to be capable of both absolute and relative dominance, and within species-specific limits the balance may shift toward one or the other. High density, or a decrease in available resources, favours a shift from relative to absolute dominance. Some species may exhibit both simultaneously. Social mammals may have intra-group hierarchies and reciprocal territoriality between groups, while the males of lek species may exhibit ‘polarized territoriality’ by defending small individual territories, with the most dominant males holding the central territories where most of the mating takes place. 4. Territoriality is a form of space-related dominance. Most biologists agree that its most important function is to provide the territory holder with an assured supply of critical resources. Territoriality is selected for only when the individual's genetic fitness is increased because its increased access to resources outweighs the time, energy, and injury costs of territorial behaviour. 5. Territoriality was first defined narrowly as an area from which conspecifics are excluded by overt defence or advertisement. The definition has been variously expanded to include all more or less exclusive areas without regard to possible defence, and finally to include all areas in which the owner is dominant. I define territory as a fixed portion of an individual's or group's range in which it has priority of access to one or more critical resources over others who have priority elsewhere or at another time. This priority of access must be achieved through social interaction. 6. My definition excludes dominance over individual space and moving resources, and includes areas of exclusive use maintained by mutual avoidance. It differs from most other definitions in its explicit recognition of time as a territorial parameter and its rejection of exclusivity and overt defence as necessary components of territorial behaviour. There is an indivisible continuum of degrees of trespass onto territories, and functionally it is priority of access to resources that is important rather than exclusive occupancy. 7. There is a similarly indivisible continuum in the intensity of behaviour needed to achieve priority of access to resources. Deciding whether or not an exclusive area is defended leads to the pointless exercise of trying to decide which cues indicating the owner's presence are conspicuous enough to merit being called defence. Concentrating on overt defence emphasizes the aggressive aspects of territorial behaviour rather than the equally or more important submissive aspects such as passive avoidance.     

ENDOMORPHIC AND ECTOMORPHIC CHARACTERS IN PELECYPHORA AND ENCEPHALOCARPUS

Boke , Norman H. (U. Oklahoma, Norman.) Endomorphic and ectomorphic characters in Pelecyphora and Encephalocarpus. Amer. Jour. Bot. 46(3) : 197-209. Illus. 1959.—Outstanding ectomorphic characters of Pelecyphora valdeziana include its small size; pectinate, hairy spines; broad, truncate, floral buds; dehiscent, berry-like fruits; and black, tuberculate seeds. The leaves are vestigial, and although the areole meristem originates on the adaxial face of the tubercle primordium, it is soon elevated to the summit by intercalary growth. The first primordium of the single, elliptical series of spines is initiated immediately in front of the rudimentary leaf. Others form in acropetal sequence on either side of the areole meristem. The last ones form across the areole, leaving a meristem, which may be floral or vegetative, on the anterior side. Whether areoles of P. valdeziana can be considered dimorphic is doubtful. However, they approach the type of dimorphism found in Epithelantha. Pelecyphora aselliformis has acuminate floral buds; dry, papery fruits; and brown, curved, reticulate seeds. The leaves are reduced almost to extinction. The areole meristem becomes separated into spiniferous and axial portions early in ontogeny, but the 2 parts remain connected by a band of trichomes, which probably represents a vestigial groove. The axial meristem may be reproductive or vegetative. The sequence of spine initiation in P. aselliformis is unusual in that it begins at the anterior side of the spiniferous meristem and proceeds toward the posterior side. Areoles in this species are clearly dimorphic, much as in the mammillarias, but the vestigial groove is reminiscent of Coryphantha and related genera. Although adult specimens of Encephalocarpus strobiliformis bear scale-like tubercles, which are very different from the laterally compressed tubercles of P. aselliformis, their flowers, fruits, and seeds are almost identical. The two species share the same type of areole dimorphism, including the vestigial groove. Tubercles on seedlings and young branches of E. strobiliformis are prismatic rather than scale-like. Since they tend to be laterally compressed at the summit and bear elliptical areoles with many more spines than the adult, they resemble seedling tubercles of P. aselliformis. Tubercles on adult specimens likewise resemble each other in the structure of the epidermis and hypodermis. It does not seem possible that P. valdeziana can be retained in the genus Pelecyphora. If seed structure has any systematic value, the species belongs in or near the genus Thelocactus, to which it was assigned by Bravo. Pelecyphora aselliformis and Encephalocarpus strobiliformis, on the other hand, share so many important characters that they could well be considered cogeneric. Both seed structure and the rudimentary grooves on the tubercles suggest that their affinities may lie with certain coryphanthas or mammillarias rather than with Ariocarpus and Epithelantha.     

TEMPERATURE AND HEART RATE IN PTEROTRACHEA AND TIEDEMANNIA

1. For the heart rate in Pterotrachea coronata, intermediate temperatures disclose a thermal increment of 11,200 ±. This value is identical with the one reported by Crozier and Stier for the lamelli-branch, Anodonta. In the pteropod, Tiedemannia neapolitana the same temperatures typically reveal in the heart rate a µ value of 16,200 ± This agrees quantitatively with 16,300 found by Crozier and Stier for the heart of the slug, Limax maximus. 2. At high temperatures the average value of µ for Pterotrachea is 7,300: for Tiedemannia, 7,400. The corresponding averages at the lower limits are 22,000 and 23,000. 3. The great variability found near the edges of the temperature field are explicable in two ways. During intermissions characteristic of high temperatures and occurring also at low, we can assume a restorative process; while at both the upper and lower limits we may, in addition, find that reactions assume control which under ordinary circumstances never do so. Special evidence indicates that the highest temperatures employed, 27°C., and the lowest, 4°C., caused no irreversible changes in mechanism. 4. The theoretical analysis of the experimental facts makes use of Meyerhof''s conception of carbohydrate metabolism and projects the cyclical nature of rhythm into the substrate of control. Assuming as a source of energy an original supply of material O, the value of 22,000 ± is assigned provisionally to a mobilization hydrolysis while 11,200 ± and 16,000 ± are attached to oxidative reactions influenced respectively by OH'' and possibly Fe, or some other catalyst. The lowest value, 7,300 ± is assumed to indicate a synthetic process (lactic acid → glycogen?), possibly limited by CO₂ excretion. In the present state of our knowledge, this distribution and interpretation seems to account reasonably for the experimental facts, but until we know more about the neurogenic controls, is entitled to rank only as an hypothesis.     

ECOLOGY AND PHYSIOLOGY OF HIBERNATION AND OVERWINTERING AMONG FRESHWATER FISHES, TURTLES, AND SNAKES

1. Freshwater fishes are the most northerly of freshwater ectotherms, followed by frogs. North American freshwater snakes, turtles, and salamanders do not range farther north than southernmost Canada. 2. Freezing and desiccation are the main challenges during terrestrial hibernation of ectotherms. Oxygen depletion, water balance, and ionic balance are the major problems for air breathing ectotherms that hibernate underwater. 3. The importance of accumulation of energy stores for overwintering among fishes depends upon the length and severity of the winters, whether or not there is springtime reproduction, body size, latitude, and the availability and use of food during overwintering. 4. Fishes can decrease energy demands during the winter by reductions in activity, metabolic depression, and entrance in semi-torpidity. 5. Adaptations for coping with hypoxia and anoxia among overwintering freshwater fishes may include metabolic depression, a decrease in blood O₂ affinity, microhabitat selection, air breathing, short-distance migration, biochemical modifications aimed at adjusting glycolytic rates, and alcoholic fermentation. 6. Freshwater turtles have a worldwide northern limit of approximately 50° N, which means that some species spend about half of their lives hibernating. 7. Aquatic turtles normally hibernate underwater, although occasionally they hibernate on land. In water they usually hibernate in a hypoxic or anoxic (mud) environment and in relatively shallow water. Wintertime movements of unknown frequency occur in some species. 8. The hatchlings of many turtle species can overwinter in the nest. Among northern species this behaviour is most common among painted turtles, whose hatchlings can withstand freezing. 9. Mortality among adult turtles is probably highest during the hibernation cycle. 10. Temperature appears to the most important cue for entry and exit from hibernation among freshwater turtles. 11. Little is known of the energetics of overwintering turtles. Energy stores for overwintering may be more important at lower latitudes than at higher ones, due to the higher metabolic rates of overwintering, but non-feeding, southern turtles. 12. The ability of turtles to tolerate submergence is a function of temperature, degree of water oxygenation, latitude of origin, efficacy of extrapulmonary respiratory pathways, and metabolic rate. 13. For turtles that hibernate in an anoxic hibernaculum, and for those without sufficient extrapulmonary uptake of O₂ to allow metabolism to be completely aerobic, the most important physiological perturbation is an acidosis developed from a continuing production of lactate. If sufficient O₂ can be obtained, the most likely factors limiting hibernation time are water balance and ion balance. 14. Mechanisms of turtles for coping with acidosis include metabolic depression, integumental CO₂ loss, bicarbonate buffering, and changes in ion concentrations that minimize the decrease in SID (strong ion difference). The most important among the latter are a decrease in plasma [Cl^-] and large increases in plasma calcium and magnesium. 15. Turtles are unique among reptiles in their ability to maintain both cardiovascular and nervous system function during prolonged anoxia. 16. Turtles gain weight from water uptake during submerged hibernation, but apparently maintain some kidney function; however, osmoregulation is one of the least known areas of the physiology of hibernation. 17. Recovery of turtles upon emergence commences with a rapid hyperventilatory compensation of pH, followed by a slower adjustment of ion levels. Basking speeds recovery greatly. 18. While hibernation of turtles in the northern parts of their ranges is most likely very stressful physiologically, northern range limits are more likely to be determined by reproductive restraints than by the rigors of extended hibernation. 19. The superior ability of turtles to tolerate anoxia may be more the result of an annual hibernation than of their diving habits during active periods of the year. 20. Freshwater snakes usually hibernate on land. However, they appear to be capable of aquatic hibernation and may not do so because of the risk of death from anoxia. 21. Some species of terrestrial snakes are known to hibernate underwater, and are able to do so in the laboratory for months. In the field, this behaviour is considered opportunistic, as there is no evidence to suggest that any snakes can tolerate extended anoxia.     

NEW AND RARE CHRYSOPHYTES FROM WYOMING AND COLORADO LAKES

Colorado and Wyoming lakes with high pH values generally ranging from 8 to 10 are dominated by phytoplankton belonging to the chrysophytes, diatoms and cryptomonads. Our studies on phytoplankton diversity in Dowdy, South Delaney Buttes and Cowdrey Lakes in Colorado and Diamond and Twin Buttes Lakes in Wyoming have yielded several isolates of rare or new chrysophytes. These isolates were examined with light microscopy, SEM, TEM, and novel information regarding their structure is presented. Proposed new species belong to the genera Saccochrysis, Prymnesium and Chrysochromulina. Chrysophytes that were examined for the first time include Monochrysis aphanaster , Uroglenopsis , and a mixotrophic species of Ochromonas , which ingests small diatoms. Probable new species are the following: Saccochrysis sp. nov. differs in chloroplast structure, cell shape and cell number/colony, and absence of a posterior vacuole; Prymnesium sp. nov. is the first freshwater form examined with EM and differs in scale morphology; and Chrysochromulina sp. nov. is similar to Chrysochromulina parva but lacks scales. The ultrastructure of M. aphanaster is unique and appears to be a member of the Chrysophyceae. It has two flagella, one of which is emergent, while the other is hidden within an invagination of the cytoplasm. Diacronema and Sarcinochrysis spp. from these lakes also were isolated and reinvestigated, and some unique cellular features will be discussed.     

NUTRIENTS AND THE PRODUCTIVITY OF ESTUARINE AND COASTAL MARINE ECOSYSTEMS

SUMMARY

Recent research on estuarine and coastal marine systems has revealed two particularly interesting things about nutrients and productivity. First is the observation that these areas are among the most intensively fertilized environments on earth. Second is the common finding that much of the characteristically high primary productivity of these shallow waters is supported by nutrients released or recycled by pelagic and benthic microheterotrophs. Since nutrient inputs to coastal areas have probably been increasing and are likely to continue to do so, it is particularly important to understand the relationship between nutrient loading and nutrient cycling and the extent to which their interactions may set the levels of primary and secondary production in coastal systems.

That some direct relationship exists between the input of nutrients and the productivity of higher trophic levels has been a principle of marine ecology since the turn of the century. It is surprisingly difficult, however, to find quantitative evidence showing that estuaries, lagoons, or other coastal waters respond to eutrophication by producing a larger biomass of animals. Part of this difficulty arises because the amount of nitrogen or phosphorus incorporated in animal tissue is a very small term in the total nutrient budget of an estuary, and the accuracy and precision of ecological field measurements may not be adequate to the task. In addition, the response of natural systems to nutrient enrichment is compounded by changes in climate, hydrography, harvesting effort and technology, and pollution.

Attempts to avoid some of these problems by carrying out controlled nutrient addition experiments in the field or with mesocosms have been much rarer in marine ecology than in limnology. The results that are available for such studies seem to suggest that there is a modest enhancement of primary production with nutrient addition, but that most of this extra organic matter is rapidly consumed, presumably by microheterotrophs. In other words, as nutrient inputs rise, so does the rate of nutrient recycling. Only a small fraction of the added nutrients appears as an increment in the production of higher trophic levels.     

沙地植物柄扁桃的生物学特性及引种栽培的研究

通过研究发现柄扁桃具有典型旱生植物的形态结构特征。同时,在生理特征上也与旱生环境相适应。因此,在沙区引种栽培柄扁桃是可行的。柄扁桃的繁殖主要采用播种法,利用沙藏催芽法处理种子,树苗当年可出圃造林。沙地造林采用植前造林法,将株高４０—１００ｃｍ的健壮苗在春季栽植于平缓的沙地、沙丘迎风坡下部或丘间地等风蚀轻、水分条件好的沙地。     

短柄五加大,小孢子发生和雌,雄配子体发育的研究

短柄五加花药５枚,每个花药四个花粉囊。小孢子母细胞减数分裂时,胞质分裂为同时型,产生正四面体形的四分体。花药壁由表皮、药室内壁、中层和绒毡层四层细胞组成,其发育类型为双子叶型。腺质绒毡层,其细胞为二核。三细胞型花粉。子房５室,每室两个胚珠,上胚珠败育,下胚珠可育。下胚珠倒生,具单珠被,厚珠心。大孢子母细胞减数分裂形成线性排列的四个大孢子,雌配子体发育属蓼型。开花当天,花粉散开,雌配子体尚未成熟,处     

GUSTATORY REACTION TIME AND TIME INTENSITY MEASUREMENTS OF TREHALOSE AND SUCROSE SOLUTIONS AND THEIR MIXTURES

Dynamic sweetness perception of commercial food grade trehalose, sucrose solutions and their mixtures were studied for a wide range of concentrations. For gustatory reaction time (GRT), concentrations ranged from 2.3 to 13.8% for sucrose and up to 23.0% for trehalose. For time intensity (T-I) sucrose or trehalose solutions (concentration range 2.3–36.8%) and their combinations (23.0 and 36.8% total solids) were analyzed. Trehalose had bigger GRT along the studied range. Both sugars presented similar values for persistence and times of plateau and to maximum intensity, while a significant difference was observed in intensity and GRT at equal concentrations. Trehalose had longer persistence than sucrose in equi -sweet solutions. Overall sweetness profile of some sucrose solutions (i.e., 29.9% sucrose solution and 0.6 sucrose/trehalose ratio mixture at 36.8% total solids) were perceived as similar to mixtures of sucrose/trehalose or single trehalose solutions, which suggests the possibility of sugar replacement without completely modifying sweetness perception.

PRACTICAL APPLICATIONS

It has been suggested that trehalose may be a potential substitute for sucrose and other sugars used in food formulation because, although its chemical structure is very similar to that of sucrose, it is more stable at low pH and high temperatures. It is not involved in caramelization and does not participate in Maillard reaction with amino acids/proteins. In order to fully establish the potential of trehalose as a functional replacement of sucrose we have determined the sweetness dynamic profile (gustatory reaction time and time-intensity curves) of trehalose solutions and sucrose/trehalose solutions; this aspect is needed for adequately replacing (partially or totally) sucrose in food systems.     

WETLANDS AND AGRICULTURE

SUMMARY

Emphasis is given to the importance of wetlands and the need for a rational and multi-use approach to their development. Their occurence in the landscape is explained and a brief account is given of characteristic soils and other related features.

Wetlands are widely distributed in certain landscapes and generally have high agricultural potential, especially for the production of cultivated pastures. A large proportion of the vleis in Natal have already been developed.

Important principles and procedures to be considered in planning wetland development are presented. The urgent need to develop a wetland strategy, initiate appropriate research, apply effective legislation and identify wetlands in need of total protection is stressed.     

PHAGE-MEDIATED SELECTION AND THE EVOLUTION AND MAINTENANCE OF RESTRICTION-MODIFICATION

Restriction-modification (R-M) was discovered because it provides bacteria with immunity to phage infection. But, is phage-mediated selection the sole mechanism responsible for the evolution and maintenance of these ubiquitous and multiply evolved systems? In an effort to answer this question, we have performed experiments with laboratory populations of E. coli and phage and computer simulations. We consider two ecological situations whereby phage-mediated selection could favor R-M immunity; i) when bacteria with a novel R-M system invade communities of phage-sensitive bacteria in which there are one or more species of phage, and ii) when bacteria colonize bacterial-free habitats in which phage are present. The results of our experiments indicate that in established communities of bacteria and phage, the advantage R-M provides an invading population of bacteria is ephemeral. Within short order, mutants resistant (refractory) to the phage evolve in the dominant population and subsequently in the invading population. The outcome of competition then depends on the relative fitness of the resistant states of these bacterial clones, rather than R-M. As a consequence of sequential selection for independent mutants, this rapid evolution of resistance occurs even when two and three species of phage are present. While in our experiments resistance also evolved when bacteria colonized new habitats in which phage were present, a novel R-M system greatly augmented the likelihood of their becoming established. We interpret the results of this study as support for the hypothesis that the latter, colonization selection, may play an important role in the evolution and maintenance of restriction-modification. However, we also see these results and other observations we discuss as questioning whether protection against phage is the unique biological role of restriction-modification.     

ADVANTAGES AND DISADVANTAGES OF EGRET AND HERON BROOD REDUCTION

Data from great egrets and great blue herons were used to test a fundamental assumption of Lack's brood-reduction hypothesis, that mortality is brood-size dependent. This was confirmed for the largest brood sizes (4 and 3), which, in egrets, also have the highest sib-fighting rates. Broods of one, however, experienced paradoxically high mortality, especially early in the season. The hypothesis is advanced that parents desert unprofitably small broods when sufficient time remains for production of a larger brood. A simple game-theory model shows that this parental desertion may hinge primarily on the overall costs of renesting. Egret brood reduction caused by sibling aggression (siblicide) occurred later than less aggressive forms of brood reduction. The inclusive fitness of senior broodmates is maximized by the successful fledging of all sibs, and the physical superiority of seniors (in food-handling for herons; food-handling and aggression for egrets) usually suffices to guarantee their own welfare in brood competitions. Finally, it is shown that the last chick in asynchronously hatching broods represents two kinds of reproductive value (RV) to the parents—“extra RV” (obtained despite the survival of elder sibs) and “insurance RV” (obtained only when at least one elder sib dies first)—which can be distinguished from field data. This approach can be used in comparisons with other asynchronous species for partitioning the fitness contributions of marginal offspring.     

ON THE COEXISTENCE AND COEVOLUTION OF ASEXUAL AND SEXUAL COMPETITORS

The coexistence and coevolution of sexual and asexual species under resource competition are explored with three models: a nongenetic ecological model, a model including single locus genetics, and a quantitative-genetic model. The basic assumption underlying all three models is that genetic differences are translated into ecological differences. Hence if sexual species are genetically more variable, they will be ecologically more variable. Under classical competition theory, this increased ecological variability can, in many cases, be an advantage to individual sexual genotypes and to the sexual species as a whole. The purpose of this paper is to determine the conditions when this advantage will outway three disadvantages of sexuality: the costs of males, of segregation, and of the additive component of recombination. All three models reach similar conclusions. Although asexuality confers an advantage, it is much less than a two-fold advantage because minor increases in the overall species niche width of the sexual species will offset the reproductive advantage of the asexual species. This occurs for two reasons. First, an increase in species niche width increases the resource base of the sexual species. Second, to the extent that the increase in niche width is due to increased differences between individuals, a reduction in intraspecific competition will result. This is not to imply that the sexual species will always win. The prime conditions that enable sexual species to stably coexist with or even supplant an asexual sister species are:

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数学形态学是用数学方法描述或分析一个物体图象的形状的理论和方法,是图象处理和图象识别技术的发展,但在生物学当中的应用还很有限。本文介绍了一个新的分支学科——昆虫数学形态学,包括三方面的内容：①昆虫数学形态学技术研究,涉及昆虫图象数字化技术和昆虫图象处理与识别技术;②昆虫数学形态学理论研究,主要以昆虫图象的解释和理解研究及昆虫数学形态学与分类学等学科的关系研究为主;③昆虫和昆虫数学形态学应用基础研究,涉及昆虫数学形态学数据库及其分析软件开发,昆虫图象的机器学习和计算机视觉等内容。昆虫数学形态学理论和方法与计算机视觉技术相结合,在害虫虫情监测、昆虫多媒体专家系统的构建等方面具有广阔的应用前景。     

WHOLE- AND PART-FLOWER SELF-POLLINATION IN GLYCINE CLANDESTINA AND G. ARGYREA AND THE EVOLUTION OF AUTOGAMY

The overall rate of self-fertilization can be viewed as the sum of two distinct processes: 1) self-pollination of all ovules in a flower (whole-flower self-pollination); and 2) self-pollination of some of the ovules in a flower, occurring together with outcrossing of the remaining ovules (part-flower self-pollination). In some situations these processes may be equated with different modes of self-pollination. A model of the mating system in which the progeny of separate fruits serve as the unit of observation is presented. The model partitions the overall rate of self-pollination into components attributable to whole- and part-flower selfing. When the mating system is estimated using information on marker genotypes from chasmogamous fruits in two species of Glycine together with the whole- and part-flower selfing model, the results indicate that the chasmogamous flowers in a subalpine population of G. clandestina underwent a significant level of whole-flower selfing, whereas in another, lower elevation population of G. clandestina and in a subtropical population of G. argyrea, they did not. This difference is thought to be related to the contrast in the variability of environmental conditions for insect-mediated pollination between the habitats sampled. In particular, the large component of whole-flower selfing observed in the subalpine population of G. clandestina may be due to self-pollination that is induced during periods unfavorable to insect-mediated pollination. It can be demonstrated that such induced selfing will be selected whenever environmental conditions are such that pollinator activity limits seed set, and moreover that induced selfing can result in the selection of overall levels of self-pollination that are intermediate between 0 and 1. Monte Carlo simulation is employed to show that ignoring the correlation of self-fertilization events that result from whole- and part-flower selfing may lead to biased estimates of mating system parameters.